This invention relates in general to shredders.
Shredders typically include a housing with a cutting mechanism for shredding media, e.g. cutting paper, and typically include a container for collecting shredded media, e.g. cut paper. The housing generally defines an opening through which papers to be shredded may pass to the cutting mechanism. Typically, the papers are then shredded by the cutting mechanism and collected in the container.
Some paper shredders include a media detector which may provide input to a shredder control device to allow the shedder to run at only certain times, such as when the presence of papers to be shredded is detected in the opening in the housing. One type of media detector includes an infrared (IR) emitter and sensor opposite one another across the opening.
It is know that the effectiveness of such IR based detector systems may diminish over time, for example, because of degradation of the emitter or sensor or because of the buildup of foreign material, such as paper dust, on the emitter or sensor. One known way to adjust for this diminished effectiveness is to compare a sensed IR value with the emitter on and the opening unobstructed and compare that value to a stored desired value. The power to the emitter may then be increased until the sensed value matches the desired value and then the IR emitter is reset to operate at that new power value.